A helmet for impact protection

ABSTRACT

A helmet for protecting a wearer&#39;s head has a protective layer configured to, when the helmet is impacted by a force, absorb the normal component thereof by compression and rupture when the tangential component of the force exceeds a predefined threshold.

FIELD OF THE INVENTION

The present invention generally relates to protective headwear. Morespecifically, the present invention relates to helmets protecting awearer's head against impacts.

BACKGROUND OF THE INVENTION

To prevent or reduce injuries when a person risks impacting his head,for example in sporting or industrial environments, a helmet is used forabsorbing energy caused by the impact, thereby safeguarding the brain.For example, helmets are customarily used when cycling, skiing, playingice hockey, or any other activity during which a person risks on fallingwith his head on the underground, and/or be hit by an object, such as ahockey puck.

A helmet typically comprises a shock absorbent material as an inner padto absorb energy upon impact. Generally, an outer casing or outer shellcovers the inner pad for purposes of additional protection, smoothaerodynamic characteristics and aesthetic reasons.

A force impacting the outer shell comprises in real life situations botha normal and a tangential component. The two components will then betransferred to the inner pad. Subsequently, the normal component causesa linear impact on the wearer's head by pushing on it, depending on thelinear absorbing characteristics of the inner pad and the magnitude ofthe force. The tangential component on the other hand causes arotational movement of the brain within the skull, depending on thedirection and, likewise, the magnitude.

Since brain injuries caused by a rotational impact are differentcompared to those caused by linear impacts, and are severe like bridgingvein rupturing, acute subdural hematoma, and diffuse axonal injury, ahelmet may be designed in such a way that it reacts differently based onthe magnitude and direction or angle of the impacted force on thehelmet.

In WO2015089646A1 such a helmet is disclosed comprising an inner padconfigured to react differently on the normal and tangential componentof an impacted force. Hereto, the inner pad comprises a complexarrangement of a variety of materials arranged as shock absorbersconnected to an array of connectors which deform elastically in responseto a tangential component of an impacted force. Hereby, the outer shellof the helmet can move relatively to the shock absorbers such that thetangential component will only partly be transferred to the wearer'shead, thereby reducing the risk of an injury due to a rotationalrotation of the brain. It is however a disadvantage that the helmet ishard to assemble due to the complex arrangement.

Another solution is disclosed in US20040168246A1 wherein a tangentialcomponent of an impacted force is absorbed by rigid rupturing meanslocated at different locations of the helmet such as, for example, theextremities thereof. The rupturing means rigidly connect the outer shellof the helmet to an inner shell and are configured to rupture when thetangential component of the force impacts the outer shell by guiding theimpacted force to these means. A disadvantage however is that the outershell needs to be completely round to efficiently guide the impactedforce to the means. Furthermore, since the rupturing means fixedlyattach the outer shell to the inner layer, a solid connection arises atthese fixing points thereby reducing the capability of absorbing linearimpacts, especially at those connection points.

It is an object of the present invention to alleviate the abovedrawbacks and to provide an improved solution for reducing a risk ofinjuries due to a rotational acceleration of the brain when a helmet isimpacted by a force.

SUMMARY OF THE INVENTION

This object is achieved by a helmet for protecting a wearer's headcomprising:

-   -   a protective layer configured to, when the helmet is impacted by        a force, absorb the normal component thereof by compression and        rupture when the tangential component of the force exceeds a        predefined threshold.

The helmet protects the head of a wearer when wearing it, for example,during sporting activities, like cycling, skiing, or playing ice hockey.The helmet is thus a protective gear worn by the wearer to protect thehead from injuries, and more in particular the wearer's brain.

The helmet further comprises a protective layer. The protective layercovers the wearer's head, and has a certain thickness, which may dependon the type of activity the helmet is suitable for and the level ofcomfort it needs to provide in relation to this type of activity. Theprotective layer may further comprise ventilation holes, withoutrestricting its protective characteristics.

The protective layer is, on the one hand, configured to absorb a normalcomponent from an impacted force, thus when the helmet is impacted bythe force on its surface. The normal component is the componentcomprising a direction pointing to the head's center of gravity at thepoint of impact on the surface. This force, for example, originates froma wearer's fall on the ground with his head, or from an object hittingthe helmet, for example a hockey puck. The normal component of theimpacted force is then absorbed by compression. In other words, theprotective layer protects the wearer's head, and thus his brain, againstthe normal component by deforming elastically, or plastically dependingon the magnitude of the impacted force and the modulus of elasticity ofthe protective layer. In other words, the protective layer does nottransfer the tangential component to the wearer's head or to anadditional elastic or plastic layer but absorbs the tangentialcomponents largely by the rupturing of the protective layer.

Furthermore, the impacted force may also comprise a tangentialcomponent, depending on the angle by which the force impacts the curvedsurface and transfers it to the protective layer. The tangentialcomponent is thus the tangent component at the point of impactperpendicular to the normal component. Thus, on the second hand, theprotective layer is configured to rupture when the tangential componentof the force exceeds a predefined threshold. In other words, when thetangential component of the force exceeds the predefined threshold, theprotective layer breaks or ruptures. Thus, the protective layer absorbsthe tangential component by rupturing instead of compression.Differently formulated, the energy originating from the tangentialcomponent of the impacted force ruptures the protective layer. Thus,during oblique impacts, the effects of the tangential component aremitigated through cracking under the loading distribution that thetangential component creates.

It is an advantage that since the protective layer absorbs the normalcomponent of the impacted force by decompression over its volume, nohard nodes are present. Such hard nodes are detrimental to the wearer'shead when the force is impacted at such a node. The wearers head is thusprotected, since it is the protective layer that compresses therebylimiting the transfer of the normal component of the impacted force tothe brain of the wearer.

Furthermore, a rotational movement of the brain within the skull isprevented as well, since a transfer of the tangential component ishindered due to the absorption of the component by the rupturing.Moreover, since the protective layer may rupture, its capacity ofabsorbing a tangential component is higher compared to an elastically,or even plastically deformation. This way, a rotational movement oracceleration of the skull is prevented when the wearer falls on theground or is hit by an object. Moreover, the tangential component may beabsorbed over the whole volume of the helmet layer and doesn't have tobe firstly guided to any other means which could absorb this component.

Additionally, the rupturing has the further advantage that it becomeseasily visible that the helmet is unsuitable for further use. This way,it is prevented that the wearer continues to wear the helmet when itsprotective characteristics are significantly reduced, or even absent.Differently formulated, a continuous elastically or plasticallydeformation as a reaction to a tangential component of an impacted forceresults in a reduction of the protective characteristics of the helmet,especially when the material is frequently bended or sheared and adeterioration over time therefrom is inside the material, while thisremains invisible to the wearer, and therefore doesn't prevent a furtherinappropriate use. The rupturing on the other hand is not onlyimmediately visible, but also ensures that the helmet will no further beused when its protecting capacity may no longer be assured.

According to an embodiment, the protective layer comprises closed-cellfoam configured to perform said absorbing and said rupturing.

The protective layer is thus a light-weighted material with a solidstructure like, for example, polyethylene foam or polystyrene foam, thatis effective in absorbing a linear impact. Furthermore, by using aclosed-cell foam, the protective layer may easily be shaped in a desiredform in an efficiently and economical manner. Additionally, with aclosed-cell foam no clean-cut or sharp edges will arise when rupturingdue to the tangential component of the impacted force. In other words,the protective layer will rupture without causing harmful or dangerousspots.

The closed-cell foam material further allows to provide, besides thedesired shape, ventilation holes. Finally, the protective layer may beproduced using only one material, which reduces an occurrence of makingerrors during the fabrication process

According to an embodiment, the closed-cell foam comprises expandedbeads.

The protective layer is thus, for example, an in-mold expandedpolystyrene comprising expanded beads which may be compressed and fused.The protective layer may then be fabricated using a mixture of beadswith different characteristics to achieve the anisotropic strengthcharacteristics of the protective layer. A rupture may then be initiatedat beads having a lesser density compared to other beads. This way,zones in the protective layer may be selected which will be more proneto rupture compared to other zones, such that the helmet may be adaptedto the type of activity wherein it will be mainly used. Additionally, orsimultaneously, beads of a particular colour may be used, or even amixture of colours for aesthetic reasons or other reasons, such as, forexample, when there is a need to distinguish athletes based on thecolour of the helmet such as in team sporting. This way, there is noneed on further painting the protective layer in a desired colour, yetit may be produced directly in said colour.

According to an embodiment, the protective layer comprises:

-   -   a first layer; and    -   protuberances extending from the first layer; and        wherein the protuberances are configured to rupture from the        first layer when exceeding the predefined threshold.

In other words, the first layer and the protuberances extendingtherefrom form the protective layer, wherein the protuberances areconfigured and designed to rupture for protecting the wearer's brainagainst a rotational movement or acceleration when the tangentialcomponent of the impacted force exceeds the predefined threshold.Furthermore, the rupturing can be controlled as it will appear orinitiate at the transition between the layer and protuberances. Thisway, a good control over the rupturing characteristics by thedimensioning and number of protuberances is achieved.

The protuberances may be faced towards the wearer's head when the helmetis worn. This way, the head is in contact with the protective layer atthese protuberances, and simultaneously allowing air to flow between theprotuberances such that the head remains cool during intensive sportingactivities, and at the same time a protection against a rotationalmovement or acceleration is guaranteed.

The protuberances may also be faced away from the wearer's head suchthat the head is in direct contact with the first layer. This may alsobe beneficial, for example, when the helmet through the first layer isshaped such that it covers the head in a comfortable and safe manner,while at the outside the protuberances likewise assure a protectionagainst a rotational movement or acceleration.

According to an embodiment, the protective layer further comprises asecond layer covering the protuberances.

The second layer may cover the protuberances either on the outside whenthe protuberances face away from the wearer's head, either on the insidewhen the protuberances face towards the wearer's head. In the firstconfiguration, the protuberances are protected against externalconditions, such as rain and/or dust. Similarly, when the second layercovers the wearer's head when the helmet is worn, the second layer maybe suitable to absorb sweat during sporting activities and may easily bereplaced afterwards, thereby keeping the protuberances of the firstlayer clean.

According to an embodiment, the second layer also comprisesprotuberances configured to rupture from the second layer when exceedingthe predefined threshold.

In other words, a double protection against a rotational movement oracceleration is provided, both by the protuberances of the first and thesecond layer.

According to an embodiment, the protuberances of the first layer and theprotuberances of the second layer face towards each other.

The first or the second layer covers the wearer's head, and the otherlayer, thus the layer not covering the wearer's head is located on theoutside of the helmet. In between the two layers, the protuberances arepresent, one extending from the first layer, and one extending from thesecond layer. The protuberances of the first and the second layerprotect the wearer's brain against a rotational movement oracceleration. Additionally, this way the first and second layer mayfurther relatively move to each other, which also provides an additionalprotection against a rotational movement or acceleration. Furthermore,this way the protective layer is easily to produce, since the firstlayer with its protuberances may in a straightforward manner put on thesecond layer with its protuberances.

According to an embodiment, the first and second layer are connectedwith each other by the protuberances.

In other words, the protuberances extending from both layers facing eachother may formally or shapely correspond to each other and be arrangedon their respective layer in such a way that they may clasp with anopposite protuberance, thereby connecting the first with the secondlayer.

Advantageously, the helmet may be assembled by two parts, namely thefirst layer with protuberances and the second layer likewise withprotuberances, from which one is regarded as an outer layer, this isfacing the outside, and one layer as the inner layer, this is the layercovering a wearer's head. The inner layer may then be equal for all typeof helmets and thus economically be produced, while the outer layer maybe adapted to the type of activity it will be used for and afterwardsclasp on the inner layer.

According to an embodiment, the protuberances of the first layer areinterlinked with the protuberances of the second layer.

Preferably, the first and the second layer are interlinked or connectedthrough the protuberances. The protective layer then comprises one wholecomprising the first and second layer joined or interlinked with theprotuberances. Between the protuberances, and thus also between thefirst and second layer, air or another gas may be present, therebyobtaining a light-weighted protective layer providing protection againsta linear and rotational impact. This way, the protective layer and thusthe helmet is suitable for sporting activities wherein a light-weightedhelmet is beneficial for delivering a performance like, for example,during time trials. Moreover, the thickness of the protective layer maybe reduced by, for example, reducing the space between the protuberancesto a minimum. Furthermore, the protective layer may easily be assembled,since the protuberances of the first layer may be clicked in theprotuberances of the second layer in a straightforward manner.

It is further another advantage that, by interlinking the two layers, afixed connection is ensured such that the two layers stay connectedwhen, for example, the helmet is used during dynamically and intensivelymoves during an activity such as, for example, playing ice hockey.

According to an embodiment, the protuberances comprise at least one ofthe group of:

-   -   a tubular protuberance;    -   a beam-shaped protuberance;    -   a conical protuberance with an elliptic or polygonal base.

The protuberances may have different shapes, like tubes, beam-shapes orbars, and cones or pyramids. This way, the characteristics of theprotuberances with respect to their capacity to rupture when thetangential component is exceeded may be adapted. For example, a conicalprotuberance comprises a base and apex, whereby, through the tapered orconical configuration from its base to its apex, the characteristicschange in the longitudinal direction by its varying cross-sections.Hence, the apex will be more prone to rupture, thus prior to a rupturingof the base. This way dedicated spots in the protective layer may beselected which rupture more quickly compared to other spots.Furthermore, the bases may be elliptic, or may comprise circles,triangles, rectangles or any other polygonal. On other spots, an equalstrength over the longitudinal direction may be preferred, thereby usingtubular or beam-shaped protuberances. An alternating pattern ofprotuberances may thus arise and configured such that stressesoriginating from the tangential component are concentrated in dedicatedpositions of the protective layer.

According to another preferred embodiment, the protective layercomprises a mixture of the beads and second granules.

Alternatively, the protective layer may comprise, besides the mixture ofbeads also second granules. The second granules have a differentcomposition compared to the beads and are arranged within the protectivelayer. The granules may also be arranged within the protective layer asclusters in a predefined shape.

According to an embodiment, the protective layer is further arrangedsuch that the rupturing initiates at a border between the beads and thegranules.

By using the granules, the rupturing may be initiated at the bordersthereof, thus at the interfaces between the beads and the granules. Thisway, dedicated spots of the protective layer may be selected wherein thegranules are arranged within the protective layer, such that at theseborders or interfaces the rupturing is initiated when the tangentialcomponent exceeds the predefined threshold. Furthermore, this way abetter control is obtained of sport where an initiation of the rupturingis preferred.

According to an embodiment, the bead and granules have a diameter ofaround 0.5 mm to around 5 mm, preferable around 1 mm to around 3 mm.

In other words, the beads and the granules may have the same diametersuch that the protective layer may economically be produced bycompressing and fusing the beads and granules. Furthermore, since thegranules have an equal diameter, the beads will not be damaged by thegranules while compressing and fusing.

According to an embodiment, the beads have a first density between 50and 70 m⁻³·kg, preferably 60 m⁻³·kg; and the granules correspond tosecond beads having a second density between 90 and 110 m⁻³·kg,preferably 100 m⁻³·kg.

Differently formulated, the protective layer may also be assembled usinga mixture of beads with different densities, namely a first density ofpreferably 60 m⁻³·kg and a second density of preferably 100 m⁻³·kg. Themixture of beads is then compressed and fused, thereby shaping theprotective layer.

According to an embodiment, the mixture comprises between 25 and 75weight percent, preferably 50 weight percent of the beads with the firstdensity.

The weight percent of the beads with the second density is thendetermined by the weigh density of the beads with the first density.

BRIEF DESCRIPTION OF THE DRAWINGS

Some example embodiments will now be described with reference to theaccompanying drawings.

FIG. 1A illustrates a helmet according to an illustrative embodiment ofthe invention; and

FIG. 1B illustrates the helmet of FIG. 1A with a cross-sectional view;and

FIG. 2A illustrates a protective layer according to a first illustrativeembodiment of the invention comprising a first and second layer andprotuberances; and

FIG. 2B illustrates the protective layer of FIG. 2B comprising rupturedprotuberances; and

FIG. 3A illustrates a protective layer according to a secondillustrative embodiment of the invention comprising a first and secondlayer and protuberances; and

FIG. 3B illustrates a protective layer similar to the illustrativeembodiment of FIG. 3A comprising protuberances that are reverselyoriented; and

FIG. 4A illustrates a protective layer according to a third illustrativeembodiment of the invention comprising a first and second layer andprotuberances; and

FIG. 4B illustrates a protective layer according to a fourthillustrative embodiment of the invention comprising a first and secondlayer and protuberances; and

FIG. 5A illustrates a protective layer according to a fifth illustrativeembodiment of the invention comprising a first layer and protuberances;and

FIG. 5B illustrates the protective layer of FIG. 5A comprising rupturedprotuberances; and

FIG. 6 illustrates a protective layer according to a sixth illustrativeembodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENT(S)

FIG. 1A illustrates a helmet according to an illustrative embodiment ofthe invention and FIG. 1B illustrates the same helmet with across-sectional view. The helmet 100 is suitable to be worn duringsporting activities like, for example, cycling or skiing. When thehelmet 100 is worn, the wearer's head is in the position 107.

The helmet 100 may comprise a clasp or buckle 110 which can be wrappedaround the wearer's chin when worn to secure a safe wearing of thehelmet 100 on the head during activities. The helmet 100 may furthercomprise an outer shell 101, and ventilation holes 111. The outer shell101 may function as a protective layer against external conditions, suchas wind or rain, and the ventilation holes may function to manage a heatregulation of the wearer's head, and/or for reasons of aerodynamics,and/or aesthetics. It should be further understood that thesefunctionalities 110 and 111 are illustrative and may vary on the type ofactivity for which the helmet is designed for, or even may be absent.

The helmet 100 comprises a protective layer 106, which is illustrated inthe cross-sectional view 120 in FIG. 1B. The protective layer 106 has acurved surface 112 on the outside and it may further be covered by theouter shell 101. Alternatively, the curved surface 112 of the protectivelayer 106 may itself comprise the outer layer of the helmet 100, meaningthat there is no outer shell 101.

During activities, the helmet 100 may be impacted by a force,illustrated by the impacted force 105. This force may, for example,originate from a fall on the ground, or from a hit by an object. Themagnitude and direction of the impacted force 105 is a prior not knownbut may be presented by a vector 105 comprising a normal component 102and a tangential component 103. The vector 105 further points to point104 which represents the point of impact. It should be however furtherunderstood that the point of impact may also comprise an area or zone ofimpact depending on the surface whereupon the wearer of the helmet 100falls, or the shape and size of the object that hits the helmet 100.

The impacted force 105 is further illustrated in FIG. 2A thatillustrates the protective layer 106 comprising a first or outer layer200 and a second or inner layer 201. The protective layer 106 in thisfirst illustrative embodiment further comprises protuberances 202extending from both layers 200 and 201 and connecting the layers 200 and201 with each other.

The force 105 impacts the protective layer 106 at the outside therefromthus at the curved surface 112, and the tangential component 103 thereofis transferred to the other zones of the protective layer 106. Likewise,the normal component 102 is transferred as well to the other zones ofthe protective layer 106.

Alternatively, when the helmet 100 comprises an outer shell 101, theimpacted force 105 first impacts the outer shell 101, and the force 105is subsequently transferred to the protective layer 106.

The normal component 102 is absorbed by the protective layer 106 throughcompression. In other words, the protective layer 106 compresses suchthat the outer layer 200, the protuberances 202 and the inner layer 201come closer together during compression, and afterwards, when theimpacted force 105 is no longer present, the layers 200 and 201 andprotuberances 202 may return to their initial shape, or may be deformedplastically, depending on the magnitude of the normal component 102 withrespect to the modulus of elasticity of the protective layer 106, yetwithout breaking or rupturing.

The tangential component 103 is transferred to the body of theprotective layer 106, which is illustrated by arrow 210. Arrow 210 thusillustrates that, due to the tangential component 103 of the impactedforce 105, that a relative movement of the outer layer 200 with respectto the protuberances 202 and/or the inner layer 201 occurs.

When the tangential component 103 exceeds a predefined threshold, theprotuberances 202 of the protective layer 106 are configured to rupture.The rupturing is thus initiated by the tangential component 103 of theimpacted force 105 and depends on the angle under which the impactedforce 105 hits 104 the protective layer 106 and the magnitude thereof.

The rupturing of the protuberances 202 is illustrated by ruptures 211and rupture 212. The protuberances 202 in this first illustrativeembodiment comprises tubular or beam-shaped protuberances. Because ofthis the strength characteristics of the protuberances remain equal overtheir respective longitudinal direction. This means that theprotuberances will rupture at a spot where its cross-section is nolonger resistant to the predefined threshold. This may, for example, beat the middle of a protuberances, as illustrated by ruptures 211, or atan extremity as illustrated by rupture 212. The position will thus bedetermined by the location 104 of the impacted force 105 and the way itis transferred 210 to the protuberances 202. Depending on the magnitudeand direction of the impacted force 105, a rupturing may also occur atthe layer 200, as illustrated by rupture 213.

As a result of the rupturing, the outer layer 200 is detached 203 fromthe inner layer 201. It may further occur that only a part of theprotuberances is ruptured. In other words, the rotational impact oracceleration originating from the impacted force 105 and more inparticular the tangential component 103 thereof is then absorbed by therupturing of a part of the protuberances, while other protuberancesremain intact.

The protuberances may also comprise other shapes compared to a tubularor beam-shapes. In FIG. 3A and FIG. 3B a second illustrative embodimentof the invention is illustrated comprising conical protuberances 300such as cone 302. It should be further understood that a cone is athree-dimensional geometric shape tapering smoothly from a base to anapex, wherein the base and the apex may be circular, but may alsocomprises any other polygonal shape. The protuberances 300 may thus alsofor example comprise pyramids.

The conical protuberances 300 are connected to the outer layer 200 bytheir respective apex, as illustrated by apex 311, and by theirrespective base to the inner layer 201, such as base 310. Theconfiguration may also be reverse, this is the bases are connected tothe outer layer 200 and the apexes to the inner layer 201, asillustrated by protuberances 301 of FIG. 3B.

Due to the tapered configuration of the protuberances 300 and 301, thestrength characteristics vary because of the varying cross-sections. Forexample, when the tangential component 103 is transferred, stressesoriginating therefrom may be concentrated at the apex of the conicalprotuberances, such that the rupturing is initiated at these apexes.This is illustrated by rupture 312 at the outer layer 200, and byrupture 313 at the inner layer 201. Depending on the magnitude anddirection of the impacted force 105, a rupturing may also occur at theouter layer 200, as illustrated by rupture 314.

Besides a uniform directional arrangement of the conical protuberances,such as configuration 300 where the bases are all located at the innerlayer 201, or configuration 301 where all the apexes are located at theinner layer 201, the conical protuberances may also be arranged in analternating pattern as illustrated in FIG. 4A by protuberances 400. Inthis third illustrative embodiment, the direction of the taperedconfiguration may be altered, and the embodiment may further comprisebeam-shaped and/or tubular protuberances. In other words, the pattern ofthe protuberances may be adapted such that it comprises a variety ofshapes, cross-sections and/or arrangement.

A part of the protuberances 400 may also extend from the outer layer200, while the other part extends from the inner layer 201, whereby theouter 200 and inner 201 layer are connected to each other by theprotuberances. The protuberances of both layers 200 and 201 may also beinterlinked as illustrated in FIG. 4B by a fourth illustrativeembodiment of the protective layer 106. The protuberances 401 are shapedin such a way that they interlink or clasp with opposite protuberances.For example, protuberance 403 extending from the outer layer 200 claspswith protuberance 402 extending from the inner layer 201. As a result, apattern of interlinked protuberances 401 together with the inner 201 andouter 200 layer forms the protective layer 106.

According to a fifth illustrative embodiment, the protective layer 106may comprise one layer with protuberances extending therefrom, asillustrated in FIG. 5A and FIG. 5B. The layer 500 from where theprotuberances 502 extend may be the outer layer of the helmet 100, ormay be the inner layer, thus where the wearer's head 107 is located whenworn.

The impacted force 105 is then either transferred 503 to theprotuberances 502, or the protuberances 502 are directly impacted by theforce. The protuberances 502 are likewise configured to rupture when thetangential component 103 of the impacted force 105 exceeds thepredefined threshold. This is illustrated by ruptures 510 in FIG. 5B.

The protective layer 106 may also, according to a sixth embodiment,comprise one whole shape 600, for example, an in-mold expandedpolystyrene comprising expanded beads and granules 602. The granules 602are arranged such that the rupturing, when the tangential component 103exceeds the predefined threshold, is initiated at the borders of thegranules 602. The rupturing may then result in a rupture 601 over awhole length of the protective layer 106.

The protective layer as illustrated in FIG. 6A may also comprises onewhole shape without the granules 602 but comprising a mixture of beadswith different densities. For example, a first mixture of beads with adensity between 50 and 70 m⁻³·kg, preferably 60 m⁻³·kg, and a secondmixture of beads having a density between 90 and 110 m⁻³·kg, preferably100 m⁻³·kg. Both mixtures may then equally be divided, thus each 50weight percent, or the first mixture may have between 25 and 75 weightpercent, whereas consequently the second mixture has a weight percentagedetermined by that of the first mixture.

Although the present invention has been illustrated by reference tospecific embodiments, it will be apparent to those skilled in the artthat the invention is not limited to the details of the foregoingillustrative embodiments, and that the present invention may be embodiedwith various changes and modifications without departing from the scopethereof. The present embodiments are therefore to be considered in allrespects as illustrative and not restrictive, the scope of the inventionbeing indicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.In other words, it is contemplated to cover any and all modifications,variations or equivalents that fall within the scope of the basicunderlying principles and whose essential attributes are claimed in thispatent application. It will furthermore be understood by the reader ofthis patent application that the words “comprising” or “comprise” do notexclude other elements or steps, that the words “a” or “an” do notexclude a plurality, and that a single element, such as a computersystem, a processor, or another integrated unit may fulfil the functionsof several means recited in the claims. Any reference signs in theclaims shall not be construed as limiting the respective claimsconcerned. The terms “first”, “second”, third”, “a”, “b”, “c”, and thelike, when used in the description or in the claims are introduced todistinguish between similar elements or steps and are not necessarilydescribing a sequential or chronological order. Similarly, the terms“top”, “bottom”, “over”, “under”, and the like are introduced fordescriptive purposes and not necessarily to denote relative positions.It is to be understood that the terms so used are interchangeable underappropriate circumstances and embodiments of the invention are capableof operating according to the present invention in other sequences, orin orientations different from the one(s) described or illustratedabove.

1.-15. (canceled)
 16. A helmet for protecting a wearer's headcomprising: a protective layer configured to, when the helmet isimpacted by a force, absorb the normal component thereof by compressionand rupture when the tangential component of the force exceeds apredefined threshold.
 17. The helmet according to claim 16 wherein theprotective layer comprises closed-cell foam configured to perform saidabsorbing and said rupturing.
 18. The helmet according to claim 17wherein the closed-cell foam comprises expanded beads.
 19. The helmetaccording to claim 16, wherein the protective layer comprises: a firstlayer; and protuberances extending from the first layer; and wherein theprotuberances are configured to rupture from the first layer whenexceeding the predefined threshold.
 20. The helmet according to claim19, wherein the protective layer further comprises: a second layercovering the protuberances.
 21. The helmet according to claim 20,wherein the second layer also comprises protuberances configured torupture from the second layer when exceeding the predefined threshold.22. The helmet according to claim 21 wherein the protuberances of thefirst layer and the protuberances of the second layer face towards eachother.
 23. The helmet according to claim 20 wherein the first and secondlayer are connected with each other by the protuberances.
 24. The helmetaccording to claim 22 wherein the protuberances of the first layer areinterlinked with the protuberances of the second layer.
 25. The helmetaccording to claim 20, wherein the protuberances comprise at least oneof the group of: a tubular protuberance; a beam-shaped protuberance; aconical protuberance with an elliptic or polygonal base.
 26. The helmetaccording to claim 18, wherein the protective layer comprises a mixtureof the beads and second granules.
 27. The helmet according to claim 26wherein the protective layer is further arranged such that the rupturinginitiates at a border between the beads and the granules.
 28. The helmetaccording to claim 26 wherein the beads and granules have a diameter ofaround 0.5 mm to around 5 mm.
 29. The helmet according to claim 26,wherein the beads have a first density between 50 and 70 m⁻³·kg; and thegranules correspond to second beads having a second density between 90and 110 m⁻³·kg.
 30. The helmet according to claim 26, wherein themixture comprises between 25 and 75 weight percent of the beads with thefirst density.